// Copyright 2017 The Lynx Authors. All rights reserved.
// Licensed under the Apache License Version 2.0 that can be found in the
// LICENSE file in the root directory of this source tree.

// a small class for calculating MD5 hashes of strings or byte arrays
// it is not meant to be fast or secure
//
// usage: 1) feed it blocks of uchars with update()
//      2) finalize()
//      3) get hexdigest() string
//      or
//      MD5(std::string).hexdigest()
//
// assumes that char is 8 bit and int is 32 bit

#ifndef BASE_INCLUDE_MD5_H_
#define BASE_INCLUDE_MD5_H_

#include <algorithm>
#include <string>

namespace lynx {
namespace base {

class MD5 {
 public:
  typedef unsigned int size_type;  // must be 32bit

  MD5();
  MD5(const std::string& text);
  MD5(const char* text, size_t length);
  void update(const unsigned char* buf, size_type length);
  void update(const char* buf, size_type length);
  MD5& finalize();
  std::string hexdigest() const;
  friend std::ostream& operator<<(std::ostream&, MD5 md5);

 private:
  void init();
  typedef unsigned char uint1;  //  8bit
  typedef unsigned int uint4;   // 32bit
  enum { blocksize = 64 };      // VC6 won't eat a const static int here

  void transform(const uint1 block[blocksize]);
  static void decode(uint4 output[], const uint1 input[], size_type len);
  static void encode(uint1 output[], const uint4 input[], size_type len);

  bool finalized;
  uint1 buffer[blocksize];  // bytes that didn't fit in last 64 byte chunk
  uint4 count[2];           // 64bit counter for number of bits (lo, hi)
  uint4 state[4];           // digest so far
  uint1 digest[16];         // the result

  // low level logic operations
  static inline uint4 F(uint4 x, uint4 y, uint4 z);
  static inline uint4 G(uint4 x, uint4 y, uint4 z);
  static inline uint4 H(uint4 x, uint4 y, uint4 z);
  static inline uint4 I(uint4 x, uint4 y, uint4 z);
  static inline uint4 rotate_left(uint4 x, int n);
  static inline void FF(uint4& a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s,
                        uint4 ac);
  static inline void GG(uint4& a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s,
                        uint4 ac);
  static inline void HH(uint4& a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s,
                        uint4 ac);
  static inline void II(uint4& a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s,
                        uint4 ac);
};

std::string md5(const std::string& str);
std::string md5(const char* data, const size_t length);

}  // namespace base
}  // namespace lynx

#endif  // BASE_INCLUDE_MD5_H_
